ExampleEthers.js

import { ethers, utils } from 'ethers';

let provider = new ethers.providers.JsonRpcProvider('https://kovan.infura.io/v3/your_key');
const abi = []; // https://ethereumdev.io/abi-for-erc20-contract-on-ethereum/

test('network sanity check', async () => {
    let network = await provider.getNetwork();
    expect(network.chainId).toEqual(42);
});

test('Confirm correct on-chain data DAI (18 decimals)', async () => {
    const daiKovanAddr = '0x1528F3FCc26d13F7079325Fb78D9442607781c8C';

    const tokenContract = new ethers.Contract(daiKovanAddr, abi, provider); // See bottom of page for abi

    const tokenSymbol = await tokenContract.symbol();
    const tokenDecimals = await tokenContract.decimals();

    expect(tokenSymbol).toEqual('DAI');
    expect(tokenDecimals).toEqual(18);
});

test('Confirm correct on-chain data USDC (6 decimals)', async () => {
    const usdcKovanAddr = '0x2F375e94FC336Cdec2Dc0cCB5277FE59CBf1cAe5';

    const tokenContract = new ethers.Contract(usdcKovanAddr, abi, provider);

    const tokenSymbol = await tokenContract.symbol();
    const tokenDecimals = await tokenContract.decimals();

    expect(tokenSymbol).toEqual('USDC');
    expect(tokenDecimals).toEqual(6);
});

test('Confirm checksum address conversion', async () => {
    const nonCheckSumAddr = '0xd115bffabbdd893a6f7cea402e7338643ced44a6';

    const checkSumAddr = utils.getAddress(nonCheckSumAddr);

    expect(checkSumAddr).toEqual('0xD115BFFAbbdd893A6f7ceA402e7338643Ced44a6');
    expect(nonCheckSumAddr).not.toBe(
        '0xD115BFFAbbdd893A6f7ceA402e7338643Ced44a6'
    );
});

test('Invalid checksum address conversion', async () => {
    const nonCheckSumAddr = '0xD115BFfabbdd893a6f7cea402E7338643ced44a6';
    let checkSumAddr;
    try {
        checkSumAddr = utils.getAddress(nonCheckSumAddr);
    } catch {
        checkSumAddr = false;
    }

    expect(checkSumAddr).toEqual(false);
});